[Binding of gonadotropin-releasing hormone (Gn-RH) to pituitary membranes in male rats].

The binding of gonadotropin-releasing hormone (Gn-RH) to membranes of male rats pituitary cells was studied. It appeared that Gn-RH was bound to 3 classes of sites and that the concentration in high affinity binding sites was very low. Moreover there was negatively cooperative interaction among these high affinity binding sites leading to a rapid decrease in binding affinity and consequently unmeasurable displacement of labeled hormone with large amounts of radio-inert ligand. These facts are inconsistent with the possible estimation of Gn-RH by radioreceptor assay.